Cities throughout Indiana have been impacted by unprecedented flooding this month as a result of one of the wettest opening weeks of April on record.
The flooding came about as heavy rains continued through the weekend of April 5 following severe thunderstorms and tornadoes throughout the state.
Cities including Shelbyville, Nashville and Bloomington were left with eight to 10 inches of standing water, according to WTHR-TV in Indianapolis.
In Shelbyville, a number of residents, including those living south of the Big Blue River, were ordered to evacuate as the river’s crest was expected to reach 18 feet, putting it in major flood stage, according to Jenna Martin, director of public relations for the city.
Experts say floods of this magnitude, while rare, may soon become more common.
Doug Edmonds, professor of earth and atmospheric sciences at Indiana University, has studied the East Fork of the White River which runs underneath Interstate 65 near Seymour. He said this kind of flooding happens once every 50 years.
“Such events occur when high volumes of water vapor are contained within a low pressure zone,” said Gabriel Filippelli, professor of earth science at Indiana University Indianapolis.
“Any time you get a low pressure zone, you get a high likelihood of rainfall,” he explained. “These low pressure zones are more intense than they used to be, and they stay in one location for an unusual amount of time.”
He pointed to the recent floods as an example.
“On each given day, there wasn’t a tremendous amount of rainfall, like two to three inches, but they happened three days in a row,” he said. “That’s not normal.”
He and Edmonds expect extreme flooding events to increase in frequency and intensity in the coming years.
“If we look at the last 20 years, the number of these extreme events has increased about 15%,” Filippelli said. “It doesn’t require any fancy climate model to show that it’s having local influences.”
Filippelli expects the upward trajectory in flood-resulting weather events to continue. He and other climate scientists point to climate change as a driving factor in the increasing frequency of extreme floods and other uncommon weather patterns.
As the Earth’s atmosphere warms, more water vapor is produced, which could mean heavier rainfall events and more extreme floods, he said.
“The analogy is, if you have a glass of water and you only fill it up half an inch and spill it on the floor, that’s a minor cleanup. If it fills up to the top, it requires a major cleanup,” Filippelli explained.
The question is whether or not the “glass,” — the earth’s atmosphere — will be able to hold the excess water vapor.
Filippelli recommended nature-based solutions to mitigate climate change, which include installing bioswales and protecting wetlands.
Bioswales are natural water storage areas beside streets that are able to hold excess water.
“Nature is ready and willing to help us out,” he said. “We just have to use these nature-based solutions more often.”
Wetlands are also a means of water storage. One acre of wetlands can store up to 38,000 bathtubs full of water, with a large bathtub holding 40 gallons of water, according to information from the United States Geological Survey.
In Indiana, advocates have said wetlands are under attack, pointing to recent legislation that has reduced wetland protections.
Wetlands are classified according to class; the most protected wetlands fall into Class III, the least in Class I.
The Indiana General Assembly repealed what was House Bill 1383, resulting in several wetlands being reclassified into Class I, making them more appealing for developers.
“Wetlands are our great savior,” Filippelli said. “They bail us out of trouble when it comes to flooding. We disregard them at our own peril.”
Farmers and developers in river-adjacent areas will also have to plan their activities differently, Edmonds said.
“We’ll have to rethink where we set up agriculture, industry, and homes,” he said. “It’s going to be part of our lives moving forward.”
In the Wabash Valley
The Terre Haute area got hit by heavy rains the weekend of April 5, but it didn't get the amount of water that Hoosiers farther south had to endure.
National Weather Service trained volunteers’ reports from Thursday, April 3, through Sunday, April 6, at midnight showed a low reading of 4.7 inches in northwest Vigo County and high reading of 6.63” in eastern Vigo County.
Meanwhile, observations from the weather station at the Terre Haute Regional Airport showed a month-to-date total as of Sunday night of 5.51 inches, which Pettet said is about 4.56” above normal for this period.
One death was reported during the floods locally. Roy A. Smith, 60, of Center Point, a Posey Township volunteer firefighter and a Clay County deputy coroner, was responding to a report of a motorist trapped in flooding when his car left Indiana 42 and struck a tree early April 5.
Also in the Wabash Valley, New Goshen in norther Vigo County was hit by an EF1 tornado the night of April 2. Property damage was extensive, but no injuries were reported.